How long do you try...

So, me and my partner haven't been using condoms for approx 2 years. We don't have high sex drives and are usually happy having it like 2-3 times a month (I know people will think this is redic 😂 but we're always cuddling and affectionate, we just fall asleep early lol).

So....I've been pregnant before (didn't go full term), my partner hasn't. At what point do we start worrying about our fertility? Should we do a month of properly going at it like rabbits and forcing it or is 2 years TTC without forcing and planning sex enough to be worried?

I'm worried my previous pregnancy that couldn't go full term has affected my fertility or also because he's never got anyone pregnant that he can't.

We're 25 and nearly 26, lived together for over 2 years, been together over 3...stable relationship etc and we both have careers...am I too young for them to test my fertility in the UK? When my previous situation happened I asked them to test me and they refused saying I'd have to wait..not sure what for? How does it all work?